When an opening is formed in a strip of material by a conventional punch press, a slug of scrap material which conforms in shape to the shape of the opening is produced during each operating cycle and these slugs must be removed from the vicinity of the punch and die as they are produced. When the punching operation is carried out with a conventional press having a punch on a reciprocable ram and a fixed die, with the punch and die extending vertically, the slugs produced are pushed into a passageway from the die opening and the passageway extends vertically to a suitable receptacle for the scrap slugs. If the slugs are relatively heavy, they will fall by gravity through the passageway, which can be made oversized relative to the slugs, and disposal of the slugs does not present any serious problems. However, if the slugs are relatively small and have a very slight mass, they will have a tendency to adhere to the sides of the passageway and bridge across the passageway thereby blocking it against the passage of additional slugs. As a result, a large number of compacted slugs will build up in the passageway beneath the die opening. This condition can result in the entire passageway being filled with slugs so that at some point, the punch may be broken as it attempts to push a recently-produced slug onto the compacted mass of slugs in the passageway and in the die opening.
The problem of compacting of the slugs is complicated if the opening in the strip material is formed as a notch in the edge of the material rather than as a centrally located hole in the material. When the strip is notched in a punching operation, the slugs will be of varying size from one reel of coiled strip material to another for the reason that the width of the strip will vary from one reel to another within the tolerance limits which are set for a particular strip specification. For example, the width of metal strip used in a stamping operation may vary as much as plus or minus (.+-.) 0.002 inches (0.051mm) so that the overall variation in width as between the .narrowest and the widest strips will be 0.004 inches (0.101mm). Since the slugs are produced from the edge of the strip, the size of the slugs will similarly vary from one reel of material to another. The passageway must be large enough to accommodate the largest slugs which will be produced plus a slight clearance so that the largest slugs can move freely through the passageway. If, however, relatively small slugs are being produced from relatively narrow strip material, the possibility of jamming or packing of the slugs in the passageway is increased.
In the discussion presented above, it is assumed that the press is vertically mounted and that the slugs will fall under the influence of gravity. U.S. Pat. No. 4,497,196 shows a stamping and forming machine in which the punch and die assemblies are mounted horizontally for a relative movement toward and away from each other. In machines of this type, the slug passageway must extend horizontally through the die assembly and the influence of gravity is not available for slug removal purposes.
A further problem which is sometimes encountered in punching operations is that of adherence of a slug to the punch when the punch returns to its normal position after carrying out a punching operation. If the slugs are of small mass and have a thin film of lubricant on them, the lubricant on the slugs and on the punch may cause the slugs to adhere to the punch due to surface tension effects. If such adherence occurs, during the next operation cycle, the punch will move the adhered slug against the stock material and encounter increased forces as it moves downwardly and pushes the slug against the stock which is positioned over the die opening. This condition can cause breakage of the punch and in any event, requires that the press be stopped and the jam in the punch be cleared.
The problems of slug adherence to the punch and compacting of the slugs in the slug passageway can be obviated in a conventional press by providing a suction system in the slug passageway so that the slugs will be drawn by a flow of air through the slug passageway to the outlet of the slug passageway. These suctions systems are effective; however, they occupy space in the die assembly and require compressed air lines in regions of the press where compressed air is otherwise not required. Also, it is impractical to provide suction systems in stamping and forming machines of the type described in U.S. Pat. No. 4,497,196.
The present invention is directed to the achievement of an improved slug removal and controlling system which obviates the above problems encountered in the management of control of slugs in a stamping and forming machine.